Need Help building bike rack from Fabricators and CAD guys

[b-dog]

1. Would you change tubing size or wall thickness?
2. Are there better bolt-together joint strategies?
3. Would aluminum crossbars make sense?
4. Any concern about fatigue cracking?
5. Best way to prevent wobble without welding?
6. Best mounting strategy for Avalanche bed structure?
7. Are crush sleeves worth adding?
8. Would rivnuts or backing plates be preferable?
9. Any obvious weak points in this concept?
10. Any recommendations before I move into CAD drawings?

Thanks in advance for any feedback. I’m hoping to refine this into a fully dimensioned fabrication drawing package next.

I think you've got a great start. The concepts are fairly well founded and I'm a little impressed with the Ai here.

1. I think the material is thicker than necessary if it was welded but given the prompt that you are assembling this rack, I think the sizing is appropriate. You could build it and always add more support later or take it to a shop and pay to add some welds to add some rigidity. I'm assuming the tubing is steel, no where is it defined.
2. As someone previously mentioned, 8020 is crazy expensive but this is a good use case. 8020.net has free software that will help put your design in 3D, then you can order everything cut to length and assemble the parts. It won't be engineered so you'll have to slap it and say, "that's not going anywhere"....oh, AND hope that works.
3. Sure. Less weight, more corrosion resistance. Aluminum has a fatigue limit, meaning you need to oversize the material so you get enough cycles to last a lifetime. Also it's more expensive.
4. Gussets - you have them in your design.
5. No clue, never worked on one of those trucks.
6. Sure but the fab work is considerable. Your holes will need to be drilled bigger. I think you'd also want the sleeves just a tiny bit shorter than the material width so that you're clamping the tube hard enough to grip but not too much that it's crushing the wall. It might be a fine line and hard to make those sleeves just the right length (with the available tools).
8. Not my preference, especially for the project at hand. Rivnuts can spin, especially if you don't deburr the inside edge of the hole. They don't sit flush so anything you bolt on will have a gap unless you add a relief to one side or the other.
9. Welding is probably the right way to make this but it's not the only way. Without plans, there's no way to really scrutinize the details.
10. Are you going to draw it up? Your first post indicated that you were looking for CAD advice. If you're going to pay someone to design this, I would suggest having a drawing with dimensions of what you want, graph paper would set you 5 steps ahead most.

 

[KwikFab]

Hi,
I need some help building a bike rack for two e-bikes to place over the bed in my Chevy Avalanche.

What I've initially done is put in my parameters and requests to Chat Gpt. After going back and forth a bit, It seems like this is a good basic plan.

Here's my ask, Would fabricators and CAD guys, take a look at this and help me refine this into a solid plan to build this bike rack, with schematics and any changes.

I haven't learned how to weld yet, so it's going to be a bolt together unit which is not wholly unacceptable.

I'd like to get some schematic drawings if that's not too hard to do. And advice on fabrication. I don't know if this is a ridiculous request or not. If it is, please let me know and accept my apologies. But if it's not too hard, to get some plans I think I can get this built by the end of July for a road trip.

I found some metal materials guys around me here in Denver so I can pick up the raw materials. I have the tools to cut, drill, measure, deburr, paint, assemble and install. Should be a fun project. I'll document this with photos so it could be used by others if they so choose.
Thanks,
Griff

You don't really need CAD at all here as it sounds like a very basic project.

CAD would come into play if you just need a place to organize your parts and/or dimensions as well as layout where bolt hole orientation matters and so forth. More so if you have specific items that need to be cut out on CNC plasma or fiber laser.

But really, this just sounds like something you could draw on a napkin, followed by asking what some of us would do differently IE place a gusset here, or change the angle of that tube over there, or instead of a latch, use a spring loaded pin and that sort of thing.

Speaking as a welder and fabricator that does lots of CAD - sometimes a basic design on paper is more than enough as I still do this from time to time.